There are in toy shops magnetic letters in different colours. Usually, their purpose is to help children with spelling. Here we must form the needed clue with only one colour. To do so, we must exclude the letters that form the clue from all the other colours. For example, if the clue is by the window, we want to help the children by giving them the word “window”. So, we choose to form this word with blue letters. The children will have to concentrate all blue letters (d, i, n, w, w, o) and put them in the right order.